After tests at Portland, Oregon, Mt. Tabor reservoirs produced three positive results for E. coli, the Portland Water Bureau issued a city-wide boil notice Friday morning.

The notice applies to 670,00 customers, according to Jaymee Cuti, a spokesperson from the bureau. Portland provides water for 935,000 customers in the area. 

An emergency press conference is to be held at noon pacific time Friday.

"While we believe at this time that the potential health risk is relatively small, we take any contamination seriously and are taking every precaution to protect public health," Portland Water Bureau Administrator David Shaff said in the release. 

Until a clean sample with no traces of E. coli can be provided, Cuti said the boil notice will continue. 

The boil notice tells all Portland Water Bureau customers to boil their tap water used for drinking, food preparation, brushing teeth and making ice for at least one minute. It also tells customers to throw away any old tap water.

Besides Portland Water Bureau customers, there are several other water providers that are affected by the E. coli presence. They include the following:

  • Burlington Water District
  • City of Gresham (North of I-84)
  • Lake Grove Water District
  • Lorna Portland Water
  • Palatine Hill Water District
  • Rockwood Water District
  • Tigard Water Service Area (including Durham, King City and Bull Mountain)
  • Valley View Water District
  • West Slope Water District

Although consuming the water may not be overly hazordous to the health of residents in the area, diarrhea could occur.

About 240 tests per month are done by the Portland Water Bureau. If a contamination is confirmed, the bureau releases boil notices.

Water can be contaminated when a pipe breaks or when conditions expose water to outside conditions. There's no confirmation on how the Portland water supply became contaminated yet. 

Residents can check this website to see if their home or business is affected by the boil notice.